Delegates, Events and Event Handler's

Festus Hagen · Jan 9, 2017

Hi All,

Win7, VS2017RC Community.

As a learning exercise I ported Managing a Music Collection Using Visual Basic Express and SQL Server Express to Visual C++ Managed.

However, I've bumped my head on the limits of my skills with the Delegates, Events and their Handlers searching has been little help.
So here I am seeking wisdom from the wise ones!

Questions are in C++ comments of VBcode in LoadMp3s.*, Files.* and SqlMusicManager.cpp
Summary:

In SqlMusicManager.cpp
SqlMusicManager::btnSearch_Click(...)
//AddHandler loader.FileLoaded, AddressOf Me.OnFileLoaded
//RemoveHandler loader.FileLoaded, AddressOf Me.OnFileLoaded

In LoadMp3s.cpp:
LoadMp3s::F_FileFound(...)
// RaiseEvent FileLoaded(Me, New FileFoundEventArgs(e.FoundFile))

In LoadMp3s.h
// Friend Event FileLoaded As FileFoundDelegate
// Private WithEvents F As FindFiles = Nothing

In Files.cpp
FindFiles::EnumFiles(...)
//RaiseEvent FileFound(Me, New FileFoundEventArgs(i))

In Files.h
// Friend Delegate Sub FileFoundDelegate(ByVal sender As Object, ByVal e As FileFoundEventArgs)
// Friend Event FileFound As FileFoundDelegate

Full source:

Files.h

#pragma once

ref class FileFoundEventArgs : public System::EventArgs
{
public:
FileFoundEventArgs(System::IO::FileInfo^ FoundFile)
{
this->m_FoundFile = FoundFile;
}

property System::IO::FileInfo^ FoundFile
{
System::IO::FileInfo^ get()
{
return this->m_FoundFile;
}
}

private:
System::IO::FileInfo^ m_FoundFile;
};

// Friend Delegate Sub FileFoundDelegate(ByVal sender As Object, ByVal e As FileFoundEventArgs)
delegate System::Void FileFoundDelegate(System::Object^ sender, FileFoundEventArgs^ e);

ref class FindFiles {
public:
FindFiles();
System::Void EnumDirectory(System::IO:

irectoryInfo ^ Dir);
System::Void EnumFiles(System::IO:

irectoryInfo^ Dir);
System::Void Start(System::String ^ Path);
// Friend Event FileFound As FileFoundDelegate
event FileFoundDelegate^ FileFound;

property System::String^ SearchExt
{
System::String^ get()
{
return m_SearchExt;
}
System::Void set(System::String^ value)
{
m_SearchExt = value;
}
}

private:
System::String^ m_SearchExt = "*.mp3";
};

Files.cpp

#include "Files.h"

FindFiles::FindFiles()
{
}

System::Void FindFiles::Start(System::String^ Path)
{
if(System::IO:

irectory::Exists(Path)) {
System::IO:

irectoryInfo^ i = gcnew System::IO:

irectoryInfo(Path);
this->EnumDirectory(i);
}
}

System::Void FindFiles::EnumDirectory(System::IO:

irectoryInfo^ Dir)
{
EnumFiles(Dir);
cli::array<System::IO:

irectoryInfo^>^ ds = Dir->GetDirectories();
for each(System::IO:

irectoryInfo^ i in ds)
{
EnumDirectory(i);
}
}

System::Void FindFiles::EnumFiles(System::IO:

irectoryInfo^ Dir)
{
cli::array<System::IO::FileInfo^>^ filesFound = Dir->GetFiles(this->m_SearchExt);
for each(System::IO::FileInfo^ i in filesFound)
{
//RaiseEvent FileFound(Me, New FileFoundEventArgs(i))
}
}

ID3v1Reader.h

#pragma once

ref class ID3v1Reader {
public:
ID3v1Reader();
ID3v1Reader(System::String^ FileName);
System::Void Parse();
private:
System::Void Reset();

public:
property System::String^ Artist
{
System::String^ get() {
return m_Artist;
}
System::Void set(System::String^ value) {
m_Artist = value;
}
}

property System::String^ Comment
{
System::String^ get() {
return m_Comment;
}
System::Void set(System::String^ value) {
m_Comment = value;
}
}

property System::Byte^ Genre
{
System::Byte^ get() {
return m_Genre;
}
System::Void set(System::Byte^ value) {
m_Genre = value;
}
}

property System::String^ FileName
{
System::String^ get() {
return m_FileName;
}
System::Void set(System::String^ value) {
m_FileName = value;
}
}

property System::String^ Recording
{
System::String^ get() {
return m_Recording;
}
System::Void set(System::String^ value) {
m_Recording = value;
}
}

property System::Byte^ TrackSequence
{
System::Byte^ get() {
return m_TrackSequence;
}
System::Void set(System::Byte^ value) {
m_TrackSequence = value;
}
}

property System::String^ TrackTitle
{
System::String^ get() {
return m_TrackTitle;
}
System::Void set(System::String^ value) {
m_TrackTitle = value;
}
}

property System::String^ Year
{
System::String^ get() {
return m_Year;
}
System::Void set(System::String^ value) {
m_Year = value;
}
}

private:
System::String^ m_Artist; // TPE1 Artist
System::String^ m_Recording; // TALB Album
System::String^ m_TrackTitle; // TIT2 Title
System::Byte^ m_TrackSequence; // TRCK Track
System::String^ m_Comment; // COMM Comment
System::Byte^ m_Genre; // TCON Genre
System::String^ m_Year; // TDRC Year
System::String^ m_FileName; // Filename
};

ID3v1Reader.cpp

#include "ID3v1Reader.h"

ID3v1Reader::ID3v1Reader()
{
}

ID3v1Reader::ID3v1Reader(System::String ^ FileName)
{
this->FileName = FileName;
}

System::Void ID3v1Reader:

arse()
{
if(!System::String::IsNullOrEmpty(this->FileName)) {
try
{
// Simple data for testing
m_Artist = "Artist";
m_Recording = "Album";
m_TrackTitle = "Title";
m_TrackSequence = (System::Byte)0;
m_Comment = "Comment";
m_Genre = (System::Byte)0;
m_Year = "Year";
} catch(...) {
System::Windows::Forms::MessageBox::Show("File load", "ERROR", System::Windows::Forms::MessageBoxButtons::OK, System::Windows::Forms::MessageBoxIcon::Exclamation);
}
}
}

System::Void ID3v1Reader::Reset()
{
m_Artist->System::String::Remove(0);
m_Recording->System::String::Remove(0);
m_TrackTitle->System::String::Remove(0);
m_TrackSequence = (System::Byte)0;
m_Comment->System::String::Remove(0);
m_Genre = (System::Byte)0;
m_Year->System::String::Remove(0);
}

LoadMp3s.h

#pragma once
#include "ID3v1Reader.h"
#include "Files.h"

ref class LoadMp3s {
public:
LoadMp3s();
LoadMp3s(System::String^ ConnectionString);
System::Int32^ Load(System::String^ Path);

System::Void F_FileFound(System::Object ^ sender, FileFoundEventArgs ^ e);

System:

ata::SqlClient::SqlCommand ^ GetInsertCommand();

property System::String^ Filter
{
System::String^ get()
{
return m_Filter;
}
System::Void set(System::String^ value)
{
m_Filter = value;
}
}

private:
// Friend Event FileLoaded As FileFoundDelegate
// Private WithEvents F As FindFiles = Nothing
ID3v1Reader^ mp3Info;
FindFiles^ F;
System::Int32 m_FilesFound;
System::String^ mstrConnectionString;
System:

ata::SqlClient::SqlConnection^ mcon;
System:

ata::SqlClient::SqlCommand^ mcmd;
System::String^ m_Filter;
};

LoadMp3s.cpp

#include "LoadMp3s.h"
#include "ID3v1Reader.h"
#include "Files.h"

LoadMp3s::LoadMp3s() {
}

LoadMp3s::LoadMp3s(System::String ^ ConnectionString)
{
this->mstrConnectionString = ConnectionString;
mp3Info = gcnew ID3v1Reader;
}

System::Int32^ LoadMp3s::Load(System::String^ Path)
{
this->m_FilesFound = 0;
mcon = gcnew System:

ata::SqlClient::SqlConnection(this->mstrConnectionString);
F = gcnew FindFiles;
F->SearchExt = "*.mp3";
F->Start(Path);
return this->m_FilesFound;
}

System::Void LoadMp3s::F_FileFound(System::Object^ sender, FileFoundEventArgs^ e)
{
this->m_FilesFound++;
if(mcon->State == System:

ata::ConnectionState::Closed)
mcon->Open();
if(mcmd == nullptr)
mcmd = this->GetInsertCommand();
mp3Info->FileName = e->FoundFile->FullName;
mp3Info->Parse();
mcmd->Parameters->AddWithValue("@ArtistName", mp3Info->Artist);
mcmd->Parameters->AddWithValue("@ArtistName", mp3Info->Artist);
mcmd->Parameters->AddWithValue("@RecordingTitle", mp3Info->Recording);
mcmd->Parameters->AddWithValue("@TrackTitle", mp3Info->TrackTitle);
mcmd->Parameters->AddWithValue("@TrackSequence", mp3Info->TrackSequence);
mcmd->Parameters->AddWithValue("@TrackYear", mp3Info->Year);
mcmd->Parameters->AddWithValue("@TrackGenre", mp3Info->Genre);
mcmd->Parameters->AddWithValue("@TrackFileName", mp3Info->FileName);
mcmd->ExecuteNonQuery();
// RaiseEvent FileLoaded(Me, New FileFoundEventArgs(e.FoundFile))
}

System:

ata::SqlClient::SqlCommand^ LoadMp3s::GetInsertCommand()
{
System:

ata::SqlClient::SqlCommand^ cmd = gcnew System:

ata::SqlClient::SqlCommand("AddMP3", mcon);
cmd->CommandType = System:

ata::CommandType::StoredProcedure;

System:

ata::SqlClient::SqlParameter^ prm = gcnew System:

ata::SqlClient::SqlParameter("@ArtistName", System:

ata::SqlDbType::VarChar, 30);
prm->Direction = System:

ata: